import java.text.DecimalFormat;
import java.util.Scanner;

public class Main1345 {
    public static void main(String[] args)throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        double x=2*n+3;
        double y=n*n;
        DecimalFormat decFormat = new DecimalFormat("##.0%");
        System.out.println(decFormat.format(x/y));
    }
}
